Why are resistors known as passive component?

Because resistor is not required to operating voltage.naturally resistive material like carbon is restrict of voltages.Active components means its requiered to operating voltage or Vcc or Vdd example transistor and fet etc..

A2

Passive components need no external control inputs. They have a natural effect on a voltage applied to them.

A3

Resistor are called passive component because their resistance value does not change even when the level of applied voltage or current to it is changed.also resistance value remains same when the applied voltage ac or dc.